This invention relates to proximity sensing apparatus and, more particularly, to a magnetic proximity sensing device especially adapted for use with fluid motive power cylinders.
It is well known to control various apparatus by sensing the operation of fluid motive power cylinders of either the pneumatic or hydraulic type. By sensing the presence or position of the movable piston within the cylinder, one can control the operation apparatus in response to movement of that piston or, alternately, control the length of the stroke of the fluid cylinder piston itself.
Although many type of proximity sensors have been previously devised, many require the presence of magnetic bodies within the part whose movement or proximity is being sensed in order to properly operate the proximity sensor. This is a particular problem with fluid motive power cylinders, the majority of which are manufactured without magnets in their piston bodies.
Another problem typically encountered in the use of proximity sensors with fluid cylinder is the attachment of the sensor to the body of the cylinder. For proper operation, it is necessary that the sensing apparatus be secured as close as possible to the cylinder itself. Prior known structures have included complicated, rigid structures fitting around the body of the cylinder which hold the sensor tightly against the cylinder body. However, since adjustment of the position of the sensors is often necessary when the piston stroke must be adjusted, such prior structures have often been difficult to move or adjust. Other structures have fixedly mounted the sensing apparatus at the ends of the cylinder eliminating flexibility necessary for complete utilization of the sensing apparatus.
The present invention overcomes the above problems by providing a sensing apparatus which is easily and securely attached to the existing structure of fluid cylinders without the necessity of providing additional ccomplicated, rigid structure and without the necessity of disassembling any portion of the fluid cylinder. The present invention is self-contained and does not require the addition or inclusion of magnets on any part of the body being sensed. Thus, the invention is especially useful with pre-existing fluid cylinders which do not include magnets in their piston bodies.